This invention relates to electrical apparatus for influencing the metabolic characteristics of living systems and has particular but not exclusive application to apparatus for applying a high frequency electromagnetic field to living tissue to promote healing thereof, at a sufficiently low field strength as not to produce any substantial tissue heating.
It has been known for many years that improved healing rates can be achieved by applying r.f. (radio frequency) electromagnetic fields to wounded tissue in such a manner as to produce tissue heating. This heating technique is known as diathermy.
More recently it has been appreciated that the therapy produced by an applied r.f. field is not characterised solely in terms of the tissue heating effect of the field. A discussion of this subject is given in "Healing by Electromagnetism - Fact or Fiction" New Scientist Apr. 22, 1976.
In published U.K. Patent Application No. 2027594 and corresponding U.S. Pat. No. 4,412,540 (Dr.R.H.C. Bentall) there is described a portable low power apparatus for attachment to a patient to produce therapy with an electromagnetic field which does not produce any substantial tissue heating. The portable apparatus comprises a battery driven r.f. oscillator and an antenna which is flexible to overlie an area of tissue to be treated. The apparatus thus can be attached to the patient and is left running on a continuous basis for the entire period for which it is desired to effect therapy. The portable apparatus produces an electromagnetic field typically in the frequency range 3-30 MHz, the particular r.f. frequency not being of great significance as to the efficacy of the treatment. The r.f. field is pulsed to maximise the therapeutic effect, typically so as to produce r.f. pulses 100 .mu.sec duration at intervals of 1 .mu.sec. The portable device operates at power levels typically of less than 100 .mu.W cm.sup.-2 as measured at the skin of the tissue, and thus at a level which does not produce any substantial tissue heating.